This invention relates to a high volume manufacturing process for continuously coating and inspecting drawn metal parts as part of a continuous series of operations to produce finished drawn metal parts. An example of high volume manufacturing of drawn metal parts is the production of battery cans, which are used as the primary battery casing for commercial cells, such as A, AA, AAA, C, D, F, M, etc.
Manufacturing of battery cans according to the prior art is generally accomplished by a batch and queue process in the following manner. A redraw press accepts narrow strip stock from a payoff reel and performs blanking, cupping and subsequent redraw operations. The entire battery can is manufactured in each stand-alone redraw press and the cans are collected in bulk in containers. The press operator and/or toolmaker manually inspect the dimensional and cosmetic attributes of the can. A pre-determined number of cans are removed randomly and inspected. Next the containers of parts from the press are moved to a staging area near a washer/dryer machine. The washer/dryer, which removes the drawing lubricant, is typically a rotary bulk washer with a cob dryer. An operator feeds the cans into the inlet of the washer. The washed cans are caught in bulk hoppers or cartons.
Next the washed cans are moved to a staging area near a coating machine. The coating machines apply thin film of coating material to the interior of the can. The cans are dried in bulk in a curing oven. An operator feeds the cans to the coaters. The cans are inspected for proper coating and then placed into the final packaging containers.
The batch and queue process described above has several disadvantages. The narrow strip stock produces significant scrap, due to unusable material at the edge of the strip. The required coil changes to feed the narrow strip stock to the redraw press lead to inefficiencies in operation. Damage can occur due to parts contacting other parts in the batch containers. Rejection of parts due to dimensional, coating and cosmetic defects may be inconsistent due to using different inspectors.
Another disadvantage is the requirement to follow the parts produced by a particular tool through the manufacturing process by keeping track of the batch container corresponding to each tool. This is necessary in order to halt operation from a particular redraw press and take corrective action if dimensional changes occur due to tool wear. Manual operator time is required to move batch containers from one operation to the next while retaining identification of the batch with the tool producing the part.
Accordingly, one object of the present invention is to provide a continuous high volume process for coating and inspecting the coating on drawn metal parts.
Another object of the invention is to provide an improved continuous process for tracking drawn metal parts through coating operations so as to identify the coating gun that coated the parts.
Still another object of the invention is to provide an improved process for inspecting coated parts and taking corrective action to shut down the coating gun if the coating is defective.
Another object of the invention is to provide an improved process for coating and inspecting the coating on drawn metal parts, and substituting additional coating guns if a coating gun is defective.